Vessels, such as tanks, are frequently cleaned by inserting a cleaning machine, which is supplied with heated, pressurized cleaning fluid, through a access port in the vessel. The cleaning machine ejects the cleaning fluid as a high velocity jet that scours the inside walls of the tank so as to effect a cleaning action. In order to obtain as wide a coverage as possible, such cleaning apparatus frequently employ rotating nozzles that sweep around as they eject the cleaning fluid. Cleaning apparatus sold by Gamajet Cleaning Services, Inc., assignee of the current invention, achieve almost 360.degree. coverage by rotating the nozzles around two mutually perpendicular axes. In such apparatus, the rotation of the nozzles is driven by a gear train that is, in turn, driven by the incoming flow of cleaning fluid via an impeller connected to the drive shaft for the gear train. Consequently, such apparatus are sometimes referred to as fluid powered, gear driven tank cleaning machines.
One early version of a fluid powered, gear driven tank cleaning machine, known commercially as the Gamajet III, is shown in U.S. Pat. No. 3,637,138 (Rucker), hereby incorporated by reference in its entirety. In the late 1980's, Gamajet introduced the Gamajet IV cleaning machine, shown in U.S. Pat. No. 5,012,976 (Loberg), hereby incorporated by reference in its entirety, which had a relatively large maximum flow rate of 300 GPM. Like the Gamajet III, the Gamajet IV featured a gear train that comprised numerous stages of pinion and spurs gears that ultimately drove a ring gear fixed on a rotating T-housing assembly so as to cause rotation of the nozzles assembly about the first axis. A bevel gear fixed on the nozzle assembly mated with a bevel gear fixed on a stem housing, which remains stationary, so that rotation of the nozzle assembly about the first axis caused rotation of the nozzles about the second axis. The fluid inlet was formed at one end of the machine, while the gear train was disposed at the other end of the machine. The rotating nozzle assembly was disposed between the inlet and the gear train.
In order to enable the impeller to operate at an efficient speed without causing the nozzles to spin too quickly, which can result in the production of a mist rather than a strong jet, the gear trains of fluid powered, gear driven tank cleaning machines must be capable of high speed reduction. In both the Gamajet III and IV, this high speed reduction is achieved by means of a number of successive stages of spur and pinion gears. In each stage, a small input pinion gear turns a large output spur gear, thereby causing an incremental speed reduction. The output spur gear of that stage is connected to a small input pinon gear of the next stage, and so on. Unfortunately, this approach results in a relatively large gear train. Thus, the gear box of the Gamajet IV is over four inches in diameter. When combined with the nozzle housing, the width of the machine is about 6 inches so that the minimum entry opening for is over 6 inches. Consequently, such machines cannot be used in some applications, such as small tanks, which feature relatively small ports. Moreover, Gamajet IV machines were relatively heavy, approximately 30 lbs, making their manipulation during installation and use difficult.
In 1994, Gamajet introduced the Gamajet V tank cleaning machine, which is shown in U.S. Pat. No. 5,954,271 (Minh) (application Ser. No. 08/821,171), hereby incorporated by reference in its entirety. The gear train of the Gamajet V featured three stages of gears rotating within a rotating cylindrical ring gear. The first and second stages are planetary gears, while the third stage are stationary gears. A first pinion gear, which is driven by the impeller shaft, drives the first stage of planetary gears. The first stage of planetary gears drives a second pinion gear that then drives the second stage of planetary gears. The second stage of planetary gears drives a third pinion gear that then drives the stationary third stage of gears. The stationary gears of the third stage drive the cylindrical ring gear. The cylindrical ring gear drives a pinion gear that, via idler gears, drives the ring gear that rotates the nozzle assembly. As in the Gamajet IV, the fluid inlet of the Gamajet V was formed at one end of the machine, the gear train was disposed at the other end of the machine, and the rotating nozzle assembly was disposed between the inlet and the gear train.
As a result of its configuration, the gear train of the Gamajet V is housed in a gear box having a diameter of approximately only 2 inches. This is only one-half the diameter of the Gamajet IV gearbox. As a result of the reduced size of the gear box, together with the use of a compact nozzle housing, the Gamajet V can be easily inserted into a 3 inch diameter access port. In addition, the Gamajet V is relatively light weight, weighing only about 7 lbs.
While a significant advancement over prior art machines, the Gamajet V has drawbacks in certain applications. First, the diameter of the Gamajet V is still too large to enter through very small access ports, such those found in wine barrels, which have access ports that are only about 11/2 inch in diameter. Consequently, it would be desirable to develop a cleaning machine capable of being installed in access ports as small as 11/2 inches. Second, although the planetary gear box is sealed, fluid can sometimes leak into the gear box of the Gamajet V if the seals are compromised. Such leakage is more likely to occur when the machine is utilized in a vertical orientation with the fluid inlet at the top, since fluid collecting in the bottom of the machine will surround the planetary gear box. Consequently, it would be desirable to develop a cleaning machine that was more resistant to leakage of fluid into the gear box.
Although the Gamajet V's capability of operating at low flow rates has advantages in some applications, other applications require flow rates higher than the 40 GPM maximum flow rate capability of the Gamajet V. Moreover, the diameter or width-wise dimension of the machine is not the only relevant dimension. Large tanks, which require the large flow rate capability of the Gamajet IV, feature oval access ports in which the width is greater than the height, the height typically being only about 18 inches. When cleaning such tanks, the cleaning machine is sometimes assembled in the vertical orientation onto a base so that it can be gradually rolled along the bottom of the vessel during the cleaning cycle. Unfortunately, the length of a Gamajet IV, which is approximately 121/2 inches, prevents the insertion of such an assembly through the access port in the vertical orientation. As a result, the assembly, including the base unit and the cleaning machine, must be rotated 90 before being inserted through the port. This operation is difficult and awkward, due to the relatively heavy weight of the Gamajet IV machine, as discussed above. Consequently, it would be desirable to develop a cleaning machine that was light and sufficiently short to be easily installed through conventional access ports in the vertical orientation, even when mounted on a roller assembly.
Moreover, in the Gamajet V, like the Gamajet III and IV machines, cleaning fluid flowed into the nozzle assembly by flowing radially outward through a stem housing on which the nozzle assembly was rotatably mounted. This was accomplished by forming four large openings circumferentially spaced around the stem housing. Unfortunately, this arrangement can cause the flow rate of the cleaning fluid to pulse as the inlet to the nozzle assembly rotates past the openings. Consequently, it would be desirable to develop a cleaning machine with a more uniform flow rate from the nozzles as the nozzle assembly rotates about its axis.
In fluid powered, gear driven tank cleaning machines, the high torque loading imposed as a result of the combined rotation of the nozzles about two perpendicular axes can impose excessive loading on the bearing that support the nozzle assembly. This is especially true in large, high flow rate machines, which necessarily require high torque loads to establish rotation. Consequently, it would be desirable to develop a cleaning machine that was less susceptible to torque loading.
Finally, in order to maximize the torque imparted to the impeller by the incoming cleaning fluid, it is important to swirl the fluid, i.e., impart a circumferential component to the fluid velocity, before it reaches the impeller. This swirling causes the fluid to spiral into the impeller blades, rather than merely flowing axially into them. Traditionally, such swirling was accomplished by a stator vane assembly located directly upstream of the impeller. The stator vane assembly consisted of stationary vanes oriented at an angle to the impeller axis so as to swirl the cleaning fluid. Unfortunately, cleaning fluid sometimes leaks around the stator vanes, in which case all of the fluid is not swirled. This leakage reduces the torque transmitted to the rotor by the cleaning fluid. Consequently, it would be desirable to develop a cleaning machine in which the fluid was more effectively swirled upstream of the impeller.